1. Field of the Invention
The invention relates to an electrowetting display device, particularly to an electrowetting display device having a luminescence conversion mechanism.
2. Description of the Related Art
FIG. 1A and FIG. 1B show a cross-section of a display unit 100 of a conventional electrowetting display device. Referring to FIG. 1A and FIG. 1B, the display unit 100 includes a polar aqueous solution 102, black ink 104 and a hydrophobic dielectric layer 106. As shown in FIG. 1A, when a voltage is not applied to the display unit 100, the black ink 104 evenly covers a top surface of the hydrophobic dielectric layer 106, and thus ambient light is absorbed by the black ink 104 to form a dark state. In comparison, as shown in FIG. 11B, when a voltage source 116 applies a voltage to a transparent electrode 108, an interface between the hydrophobic dielectric layer 106 and the aqueous solution 102 is polarized to have high surface energy, and thus the hydrophobic dielectric layer 106 that becomes less hydrophobic enables the black ink 104 to move towards a partition wall 112. At this time, the ambient light is reflected by a base plate 114 (such as a white-colored plate) to form a bright state. Such design is power-saving because images are displayed in black and white by means of the ambient light. However, the monochromic or black and white display fails to provide colorful visual effects, and such design may cease to function when the amount of ambient light is insufficient.
FIG. 2A and FIG. 2B show a cross-section of a display unit 200 of another conventional electrowetting display device. Referring to FIG. 2A, the display unit 200 similarly has a polar aqueous solution 202, a hydrophobic dielectric layer 206, a transparent electrode 208, partition walls 212, a transparent substrate 214, and a white light 216 used as a backlight source. According to this design, the black ink shown in FIG. 1A is replaced with a combination of red ink 204R, green ink 204G and blue ink 204B. A voltage source 218 applies a voltage to the transparent electrode 208 to control the distribution of each colored ink to achieve full color display. However, such design has inferior color saturation and fails to achieve full black display. Specifically, since the area of the dielectric layer 206 covered by each colored ink are adjusted to change the intensity of its corresponding color, the remaining area not covered by the colored ink may cause leakages of white light to decrease color saturation. As shown in FIG. 2A, for a blue display unit assigned to produce a blue color, surrounding white light is, however, mixed in the blue light, and some red light and green light from adjacent display units may be also mixed in the blue light to decrease color saturation. Further, as shown in FIG. 2B, in case only the grey levels of blue light and red light are adjusted, surrounding white light and some green light are liable to be mixed in the blue light and the red light to decrease color saturation. As a result, the shift in color hue and the decrease in color saturation often occur in the conventional design. Moreover, such design fails to achieve full black display. Even additional display units made of black ink are provided, the mix of surrounding white light still results in inferior color saturation.